O presente trabalho tem como objetivo explorar o uso de técnicas de controle avançado na indústria metalúrgica. O nível de aço é uma das variáveis mais críticas para a produção de chapas ou tiras de alta qualidade no processo de lingotamento contínuo de tiras baseados em rolos duplos. Para melhorar a qualidade da espessura das tiras utiliza-se em tanque intermediário submerso na piscina formada entre os rolos duplos. São propostas três técnicas e controle de \"fuzzy\" via modelos Mamdani e Takagi-Sugeno. O modelo Mamdani é desenvolvido com base no conhecimento experimental do processo. O modelo Takagi-Sugeno utiliza uma abordagem mais sistêmica para a resolução do problema, utilizando modelos locais (linearizados) da planta não-linear que descreve o nível e escoamento do aço no tanque intermediário. Os componentes do sistema de controle empregados são discutidos e especificados. São apresentados resultados de simulação utilizando os parâmetros reais de uma planta de lingotamento contínuo instalada no IPT São Paulo. As simulações realizadas mostram que as técnicas de controle sugeridas atendem as restrições da planta e são viáveis de implementação. / This work explores the use of advanced control techniques in the metallurgical industry. The molten steel level is one of the most critical to the production of high quality steel strips in strip casting process. The strip thickness uniformity can be improved using an intermediary tundish submerse into the pool formed between the two rotating rolls. Three control techniques are considered to control the intermediary tundish molten steel level: PID, feedback linearization and fuzzy logic via Mamdani and Takagi-Sugeno models. The Mamdani model is developed with base in the experimental knowledge of the process. The Takagi-Sugeno model uses a more systematic approach for the solution of the control problem using local models for the non-linear plant that describes the level and flow of the steel in the intermediary tundish. The components of the level control system are discussed and specified. Simulation results are presented considering the real system parameters of a strip casting plant installed at IPT São Paulo. The simulation results obtained show that the control techniques suggested satisfies the constraints on the plant and can be considered for implementation.

A partir de la fin de l’Antiquité, les grands bronzessont peu à peu délaissés puis abandonnés. Il faudra attendre laseconde moitié du XVIème siècle pour voir réapparaître dans lepaysage artistique français, sous François Ier, de grandsensembles statuaires en bronze. Au coeur de ce phénomène, latechnique tient un rôle majeur et suscite plusieursinterrogations. D’abord, se pose pour cette période la questionde l’existence ou non d’une identité technique des bronzesfrançais. L’exécution d’une statue en bronze implique denombreuses étapes qui conduisent du modèle à saretranscription dans le métal. Peut-on reconnaître dans cesétapes et dans les manières de les aborder une certaine unitétechnique qui marquerait la seconde moitié du XVIème siècle,voire le début du XVIIème en France ? Inversement, remarqueton dès cette période de réintroduction différentes écolesregroupant certains sculpteurs, fondeurs, ateliers, voire liées àcertains chantiers particuliers ? Par ailleurs, la réapparition dessavoir-faire associés à la statuaire en bronze pose la questiondes origines. D’où viennent ces techniques soi-disant oubliées :d’autres centres européens, de pratiques de fonderie concernantd’autres types de production ?Dans ce travail de thèse, nous nous sommes attachés à apporterdes éléments de réponse à ces différentes interrogations. Pource faire, des études technologiques ont été menées sur troisgrands ensembles marquant cette période de renouveau dansl’art du bronze : les copies en bronze de marbres antiques parPrimatice, les Vertus du monument funéraire d’Henri II et deCatherine de Médicis, les Allégories du monument de coeurd’Anne de Montmorency.Pour compléter ce corpus, des éléments isolés ont été étudiés :la Diane chasseresse de Barthélémy Prieur, l’Apollon duBelvédère, le Gladiateur Borghèse et la Vénus Médicisattribués à Hubert le Sueur. L’objectif a été de tenter de révélerprocédés, matériaux et savoir-faire engagés, complétant ainsiles données fournies par les documents d’archives quiaccompagnent ces commandes prestigieuses. La stratégied’étude employée a bénéficié de l’expérience des travauxentrepris ces trente dernières années. Des développementsméthodologiques ont néanmoins été nécessaires pour compléterles possibilités offertes par l’étude technologique de la statuaireen bronze. Ces développements ont en particulier concerné lesnoyaux de fonderie, ces matériaux employés pour réaliser desstatues creuses. Les résultats obtenus montrent que lespremières décennies de réappropriation de la grande statuaireen bronze sont marquées par l’emploi d’un même procédé àl’épargné qui trouve racine dans les procédés employés auMoyen-âge pour la fonte de cloches ou de canons par exemple.Mais dés le XVIIème siècle, le monopole de ce procédé sembleêtre mis à mal, preuve sans doute d’une émancipation desfondeurs et d’une innovation constante. Parallèlement à cesphénomènes dont les conséquences marquent la fonte statuaireen général, les sculpteurs, les fondeurs, développent dans leursateliers des savoir-faire personnels et innovent au cas par cas,selon la nature des commandes qu’ils reçoivent. / At the end of Antiquity, the manufacture of largebronzes is progressively abandoned. It reappears during the16th century in France, under the reign of Francis I, after morethan a millennium of quasi absence. At the heart of thisphenomenon, casting techniques play a major role and raisesseveral questions. First, the technical identity of large bronzescasted during this period must be investigated. Indeed, castinga statue involves numerous steps, from the model to the finalform in bronze: are those technical steps identifiable throughthe bronze statues characteristics? Are those featurescharacteristic of the craftsmanship of 16th century? Second,can we identify particular ways of bronze crafting associatedwith different schools, composed by sculptors and, or, foundrymen? The origins of technical skills are also to be questioned,especially the provenance of forgotten techniques: Europeanneighborhood or influence of metallurgical techniquesassociated to other kind of objects?In order to answer those questions, technical studies have beencarried out. A representative body of statues has beeninvestigated: the bronze copies of antique marble statues byPrimaticcio at the Fontainebleau palace, the Virtues and theroyal praying statues from the funerary monument of Henry IIand Catherine de’ Medici and the three Personifications thatdecorate the hearth monument of Constable Anne deMontmorency. Several isolated statues have also been studiedin order to complete the body of statues: Diana the huntress byBarthélémy Prieur, Borghese Gladiator and Apollo Belvedereattributed to Hubert le Sueur.This work aims at revealing the processes, materials andknowhow involved for each steps of bronze statuesmanufacture, in order to complete the data extracted fromarchive documents associated to those prestigious royalcommissions. The employed methodology is based on theexperience on this field of research acquired since threedecades by researchers all over the world. New developmentshave also been made to improve technological studies, such asan innovative approach for the characterization of castingcores. . Data obtained from the investigated body of statuesreveal that during the first decades of the 16th century, aspecific casting technique has been used: a spare process. Thisprocess has been strongly influenced by techniques steamingfrom the late Middle-age and the early modern period. Indeed,it exhibits technical similarities with bell and canon casting.However, the uniqueness of this process is challenged by theemergence, during the 17th century, of a second technique,namely the slush process. Emancipation of foundry-men fromthe main stream technique, and will of innovation mightexplain this change of process. Simultaneously to thosetechnical evolutions, sculptors and foundry-men developspecific skills and knowhow that influence the characteristicsof their bronze statues. Moreover, case to case adaptation alsoappears to influence the bronze statues characteristicsaccording to the kind of commission charged by the craftsmen

No description available.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The production of austenitic stainless-steel pump impellers in foundries present a huge challenge mainly due to its thin-walled blades, pouring temperature, presence of junctions and chemical composition. Two different alloys were used namely nodular cast iron and austenitic stainless-steel. Nodular cast iron was used as a comparison alloy due to its excellent flowability whereas austenitic stainless-steel was chosen due to its attractive corrosion and wear resistant properties. Austenitic stainless-steel alloy showed difficulties during casting because of its chemical composition and freezing range. Thin-walled sections are more susceptible to filling defects like misrun and cold-shut. This results in high scrap rate and high processing costs during high production of thin-walled components. High pouring temperature is considered one of the most effective methods to improve filling ability of thin-walled castings. However, there is a major drawback in using this method owing to the high occurrence of shrinkage defects and hot tearing especially at junctions. 1060 aluminium was used as a benchmark to evaluate the effect of wall thickness on the filling and feeding of thin-walled Al components with complex geometry during sand casting. The aim of this dissertation is therefore to optimize casting process of sand cast austenitic stainless-steel pump impeller. Numerical modelling and additive manufacturing were used to optimize the production of this product. The use of casting simulation software combined with three-dimensional (3D) mould printing technology has enabled optimisation of casting parameters to minimise the occurrence of casting defects. Casting parameters of five test samples of complex geometry and varying thicknesses (1.0 mm;1.5 mm;2 mm;2.5 mm and 3.0 mm) were optimised using MAGMAsoft® at a constant pouring temperature of 700 °C and 1060 Aluminium as an alloy. Simulation and casting results showed that complete filling was only possible at a wall thickness of 3 mm. The simulation results showed that as the wall thickness increased from 1 mm to 3 mm the filling ability increased by 67.5 % whereas experimental casting results showed that filling ability increase by 75 %. The combination of MAGMAsoft® simulation and 3D printed moulds proved to be effective tools in predicting filling and feeding of thin-walled aluminium components during sand casting. MAGMAsoft® casting software was used to simulate metal flow and predict the degree of filling at different pouring temperatures. Test samples were cast using 1060 Aluminium alloy at temperatures of 702 °C, 729 °C, 761 °C, 794 °C, 800 °C and 862 °C. Complete mould filling was predicted at 800 °C using the simulation model and 761°C during actual casting. At temperatures above 761°C tearing at the junction was quite pronounced. An optimal of 761°C pouring temperature was found to be appropriate pouring temperature when casting thin-walled aluminum components using sand casting. MAGMAsoft® casting software proved to be an effective tool in optimizing filling and feeding of thin-walled aluminium components during sand casting. Nodular cast iron pump impeller was optimized at 1500 °C using MAGMAsoft® and 3D mould printing technology. Design variables used were feeder radius (17 mm, 18 mm, 19 mm and 20 mm), feeder height (32 mm, 33 mm, 34 mm, 35 mm) and number of feeders of (3, 4 and 5). Simulation and casting results showed a completely-filled casting. The high fluidity of nodular cast iron promotes mould filling ability and prevent any form of misrun defect. Minimum shrinkage was noted at the junctions and top surface of the casting. A new design was proposed to eliminate shrinkage defects at the junctions of the nodular cast iron pump impeller. The design used a tapered circular runner bar with straight ingates. Optimization of nodular cast iron was now done at 1390 °C with the use of MAGMAsoft® and real casting was done 1385 °C. Simulation and casting were in correlation to each other since both showed completely-filled mould cavity with no misrun, cold-shut and shrinkage porosity defect. Simulation proved to be an effective tool in optimizing filling and solidification of nodular cast iron during sand casting. Austenitic stainless-steel pump impeller was optimized at 1500 °C using MAGMAsoft® and 3D mould printing technology. A high quality mould and core print were printed with the use of Voxeljet VX1000 at a minimum period of time. Design variables used were feeder radius (17 mm, 18 mm, 19 mm and 20 mm), feeder height (32 mm, 33 mm, 34 mm, 35 mm) and number of feeders of (3, 4 and 5). An increase in feeder size and the number of feeders greatly reduced hot spot and porosity of the casting but it also reduced the casting yield. The quality of the casting was found to be inversely proportional to the casting yield. Simulation showed a completely-filled casting with actual casting showing only 50 % filling ability. High viscosity of the molten metal and thin walled blades promote quick solidification which caused misrun defects. A new design was proposed to eliminate misrun defects of the first design. MAGMAsoft® was used to optimize this design at 1550 °C. The design used a tapered circular runner bar with tapered ingates. The actual casting showed improved filling ability from 50 % to 80 % while simulation showed completely-filled mould cavity (100 %). Major factors which contributed to low filling ability of austenitic stainless-steel pump impeller were chemistry, runner system and men. Numerical modelling and additive manufacturing did optimize filling and feeding of sand cast austenitic stainless-steel pump impeller.

Made available in DSpace on 2017-07-21T20:42:39Z (GMT). No. of bitstreams: 1 Josiane Carneiro Souza.pdf: 4154319 bytes, checksum: dcde979ba587a2471aa62c75df7e7827 (MD5) Previous issue date: 2012-12-19 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / The manufacture of metal parts by molding and molded by the process in the green sand (sand base crowded with clay) is widespread in industries for its low cost and operational flexibility. A major advantage is that the materials can be reused in new molding cycles. However, when the liquid metal comes in contact with the mold, causes disabling clay locally, generating inert materials that focus on the sand and limit long cycles of reuse. Thus, there are surplus sands by adding new primary materials and the consequent need for disposal to maintain the constant flow of materials. This excess is a liability that is usually discarded in landfills. This study sought a solution to this environmental waste, by reuse in the actual molding process using the sodium silicate (Na2SiO3.XH2O)/CO2, as binder. The properties obtained from samples with waste foundry sands (WFS) and with the new green sands were compared to verify the real potential for reuse WFS and the effect of its inert components and additives. For this purpose it was evaluated the mechanisms involved in the interaction with the green sand silicate before and after reaction with CO2 in the range of 0 to 20% (by weight) mixed. Mechanical properties were evaluated before and after gassing with CO2, both with WFS and with its primary components. In this study, for microstructural characterization techniques were used for X-ray diffraction, optical microscopy and MEV/ EDS. The results showed mutually dependent mechanical properties, the morphology of the silica gel coating on the sand grains, and the composition of the mixture used. / A fabricação de peças metálicas por fundição e moldadas pelo processo em areias a verde (areia base aglomerada com argila) é bastante difundida nas indústrias pelo seu baixo custo e flexibilidade operacional. Uma das grandes vantagens é que os materiais utilizados podem ser reutilizados em novos ciclos de moldagem. Porém, quando o metal líquido entra em contato com o molde, provoca a desativação da argila localmente, gerando materiais inertes que se concentram na areia e limitam ciclos longos de reuso. Com isto, surgem excedentes de areias pela adição de materiais primários novos e a consequente necessidade de descarte para manter o fluxo constante de materiais. Este excedente é um passivo que normalmente é descartado em aterros. Este trabalho buscou uma solução ambiental para este resíduo, por meio da reutilização no próprio processo de moldagem, utilizando silicato de sódio (Na2SiO3.XH2O)/CO2, como ligante. As propriedades obtidas de amostras com areias descartadas e com as areias a verde novas foram comparadas entre si para verificar o real potencial de reutilização da ADF e o efeito de seus componentes inertes e aditivos. Para esta finalidade avaliou-se os mecanismos envolvidos na interação da areia a verde com o silicato, antes a após reação com CO2, na faixa entre 0 a 20% (em peso) nas misturas. Propriedades mecânicas foram avaliadas antes e após a gasagem com o CO2, tanto com areia descartada de fundição (ADF) quanto com os seus componentes primários. Neste estudo, para caracterização microestrutural foram utilizadas técnicas de Difração de raios X, Microscopia Ótica e Microscopia Eletrônica de Varredura/EDS. Os resultados demonstraram dependência mútua entre as propriedades mecânicas; a morfologia do recobrimento da sílica gel sobre os grãos de areia; e a composição da mistura utilizada.

O presente trabalho tem como objetivo explorar o uso de técnicas de controle avançados na indústria siderúrgica. Propõe-se uma estratégia de controle do nível do aço da piscina formada entre os rolos de um sistema lingotamento contínuo de tiras (LCT) utilizando a tecnologia twin-roll (rolos duplos). O processo LCT rolos duplos tem por finalidade a produção de tiras solidificadas de espessura constante sob uma força de separação entre os rolos também constante. O nível de aço bem como a força de separação são as variáveis mais críticas para a produção de tiras de aço de alta qualidade. O nível pode ser controlado usando a entrada de aço ou a velocidade de laminação. Entretanto, a velocidade de laminação é usualmente utilizada para regular a força de separação entre os rolos. A estratégia de controle proposta inclui a incorporação de um tundish intermediário submerso na piscina. O controle do nível é então feito a partir da saída de aço do tundish intermediário. Consideramos as técnicas de controle linearizante por realimentação de estado e de controle fuzzy usando ambos os modelos Takagi-Sugeno (T-S) e Mamdani. Resultados de simulação são apresentados para uma planta instalada no Instituto de Pesquisa Tecnológica (IPT) de São Paulo, divisão de metalurgia (DIMET). / The aim of this work is to explore the use of advanced control techniques in the metallurgical industry. A control strategy to regulate the molten steellevel of a strip-casting process is proposed. The process produces a solidified strip of constant thickness given by the roll gap under a constant roll separation force. Along with the molten steel level the rool separation force are the most criticaI process variables. The molten steel level may be controlled using the tundish output flow or the casting speed. However, the casting speed is usually used to control the roll force separation. In the control strategy proposed it is incorporated an intermediary tundish submerse into the pool between the rotating rolls to improve the strip thickness uniformity. The molten steel level is thus controlled by the intermediary tundish output flow. Conventional PI, feedback linearizing plus a fuzzy control term and a fuzzy controller in a cascade configuration are considered. Simulation results are presented considering the real system parameters of a plant installed at the Instituto de Pesquisa Tecnológica (IPT) de São Paulo, Divisão de Metalurgia (DIMET).

O presente trabalho tem como objetivo explorar o uso de técnicas de controle avançados na indústria siderúrgica. Propõe-se uma estratégia de controle do nível do aço da piscina formada entre os rolos de um sistema lingotamento contínuo de tiras (LCT) utilizando a tecnologia twin-roll (rolos duplos). O processo LCT rolos duplos tem por finalidade a produção de tiras solidificadas de espessura constante sob uma força de separação entre os rolos também constante. O nível de aço bem como a força de separação são as variáveis mais críticas para a produção de tiras de aço de alta qualidade. O nível pode ser controlado usando a entrada de aço ou a velocidade de laminação. Entretanto, a velocidade de laminação é usualmente utilizada para regular a força de separação entre os rolos. A estratégia de controle proposta inclui a incorporação de um tundish intermediário submerso na piscina. O controle do nível é então feito a partir da saída de aço do tundish intermediário. Consideramos as técnicas de controle linearizante por realimentação de estado e de controle fuzzy usando ambos os modelos Takagi-Sugeno (T-S) e Mamdani. Resultados de simulação são apresentados para uma planta instalada no Instituto de Pesquisa Tecnológica (IPT) de São Paulo, divisão de metalurgia (DIMET). / The aim of this work is to explore the use of advanced control techniques in the metallurgical industry. A control strategy to regulate the molten steellevel of a strip-casting process is proposed. The process produces a solidified strip of constant thickness given by the roll gap under a constant roll separation force. Along with the molten steel level the rool separation force are the most criticaI process variables. The molten steel level may be controlled using the tundish output flow or the casting speed. However, the casting speed is usually used to control the roll force separation. In the control strategy proposed it is incorporated an intermediary tundish submerse into the pool between the rotating rolls to improve the strip thickness uniformity. The molten steel level is thus controlled by the intermediary tundish output flow. Conventional PI, feedback linearizing plus a fuzzy control term and a fuzzy controller in a cascade configuration are considered. Simulation results are presented considering the real system parameters of a plant installed at the Instituto de Pesquisa Tecnológica (IPT) de São Paulo, Divisão de Metalurgia (DIMET).

The complexity in the vehicles production process is due mainly to the large number of Assembled components that are generally characterized by a high technological content. The castings, one of these components, fit perfectly in this category and they only can be made at a competitive quality and cost level if a proper tooling is available. The molds and dies manufacturing process requires modern computer technologies and materials of high reliability and performance. Although made to mass production, toolings are unique products whose manufacturing requires technical knowledge and familiarity with the casting process where they will be employed. The selection of a casting tooling supplier is usually a complicated and time- consuming issue. The decision process is based on several criteria that can be conflicting or superposed, objective or subjective. In the present paper the analytic hierarchy process (AHP) was used to select a tooling supplier for the manufacturing of a transmission housing by the die casting process. Several qualitative and quantitative criteria for the tooling supplier selection were identified through the technical literature review and discussion with foundry specialists. Subsequently, the criteria hierarchy was established in three levels and comparison matrixes were developed to determine the priorities among them. The consistency ratio for each matrix was calculated and the final score of each potential supplier was determined. The study was concluded with a sensitivity analysis that contributed to confirm the choice of the selected supplier. The application of the methodology improved the selection process by reducing the subjectivity and by weighing the major selection criteria. / A complexidade no processo de produção de veículos deve-se, entre outras razões, aos inúmeros componentes utilizados na montagem, que em geral tem elevado conteúdo tecnológico. Os fundidos enquadram-se perfeitamente nesta categoria e somente podem ser produzidos com qualidade e custo competitivo com o emprego de moldes apropriados. A fabricação destes moldes é feita usando-se modernas tecnologias computacionais e materiais de alto desempenho e confiabilidade. Embora destinados à produção em massa, cada molde é um produto único cuja manufatura requer conhecimento técnico específico e familiaridade com o processo de fundição onde serão utilizados. A escolha de um fornecedor para moldes de fundição é normalmente um problema complicado e que consome tempo, a análise envolve múltiplos critérios, que podem ser conflitantes ou superpostos, objetivos ou subjetivos. O objetivo deste trabalho é mostrar a utilização do processo hierárquico analítico (AHP) para selecionar um fornecedor de um molde para uso no processo de fundição sob pressão, para produção de uma carcaça de transmissão. Através da revisão de literatura técnica e contatos com especialistas, diversos critérios qualitativos e quantitativos foram identificados para a escolha do fornecedor. Posteriormente estes critérios foram hierarquizados em três níveis e as prioridades entre eles identificadas em matrizes de comparação. A seguir, calculou-se a razão de consistência para cada uma das matrizes e obteve-se o escore final de cada fornecedor em potencial. O estudo foi concluído com uma análise de sensibilidade, que contribuiu para ratificar a escolha do fornecedor selecionado. A aplicação do método melhorou o processo de seleção pela redução da subjetividade e pela ponderação dos critérios julgados importantes em um fabricante de moldes complexos.

Heat transfer during metal pouring and its solidification in the vacuum furnace have been investigated by experiments using model set of castings of different diameters and insulations. The pouring metal was Inconel 713LC alloy based on nickel. The found data have been used for optimization of the numerical simulation of the thermal regime during the both pouring and solidification phases of the process in vacuum. Numerical simulation of the alloy structure in individual castings has been made by the CAFE module of the ProCast software and obtained results compared with the real structure. The optimized boundary conditions can be used for simulation of real castings.

Stochastické programování a optimalizace jsou mocnými nástroji pro řešení široké škály inženýrských problémů zahrnujících neurčitost. Algoritmus progressive hedging je efektivní dekompoziční metoda určená pro řešení scénářových stochastických úloh. Z důvodu vertikální dekompozice je možno tento algoritmus implementovat paralelně, čímž lze významně ušetřit výpočetní čas a ostatní prostředky. Teoretická část této diplomové práce se zabývá matematickým a zejména pak stochastickým programováním a detailně popisuje algoritmus progressive hedging. V praktické části je navržena a diskutována původní paralelní implementace algoritmu progressive hedging, která je pak otestována na jednoduchých úlohách. Dále je uvedená paralelní implementace použita pro řešení inženýrského problému plynulého odlévání ocelové bramy a na závěr jsou získané výsledky zhodnoceny.